(a) Technical Field of the Invention
The present invention relates to a gear-shifting structure for a vehicle, and in particular to a gear-shifting structure that integrates the operation of a clutch contained in a transmission box and a power source of gear shifting carried out by a gear-shifting hub.
(b) Description of the Prior Art
For a currently-available vehicle that is equipped with the so-called automated manual transmission (AMT), the operation of gear shifting is done by controlling an automatic clutching operator of a transmission box to cause disengagement or release of a clutch, followed by an automatic gear-shifting operator causing rotation of a gear-shifting hub to carry out gear shifting. Both the clutch and the gear-shifting hub are individually provided with an operator and a motor for carrying out the operation thereof. Thus, an AMT mechanism needs at least two sets of operator and motor. This causes an undesired constraint to the utilization of space and installing two sets of operator and motor also leads to increase of costs.
To overcome such drawbacks, an AMT system for all-terrain vehicles was developed, which, for the purposes of saving space and costs, adopts a single-motor based driving system, wherein the gear-shifting operation and the clutching operation of a clutch are respectively done by the forward and backward rotation of the motor. The motor can moves a gear-shifting hub to carry out the gear shifting operation by driving a ratcheting member and a spring back to an original position, and can use a rocker arm that is coupled to the ratcheting member to carry out the clutching operation.
The adoption of a single motor as described above, although effective in solving the problems related to spatial arrangement and costs, yet is disadvantageous in that to complete a gear shifting operation, the motor has to take operation for both forward and backward rotation. This leads to a delay in time in performing successive gear shifting operations. In addition, there still needs a number of parts and thus the problems of high costs caused by the number of parts have not been yet solved. Further, the utilization of the space inside a transmission is still subjected to undesired constraint so that expanding the size of the gear box is inevitable. In addition, the rocker arm uses the force from the ratcheting member spring to drive a clutch cam, and this leads to poor linearility of the clutch cam. In addition, transmission through the rocker arm also results in poor accumulated precision from the motor to the clutch cam.
In addition, the driving of the gear-shifting hub is done by the ratcheting member, which must be returned to the original position by the spring before the next driving can take place. In case of successive operations of gear shifting, the spring may not respond sufficiently quickly so that the successive operation of gear shifting for this type of gear-shifting system is subjected to constraint.
Thus, it is an issue to be addressed for overcoming the above drawbacks.